US7085339B2 - Data recovery device - Google Patents

Data recovery device Download PDF

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Publication number
US7085339B2
US7085339B2 US10/091,059 US9105902A US7085339B2 US 7085339 B2 US7085339 B2 US 7085339B2 US 9105902 A US9105902 A US 9105902A US 7085339 B2 US7085339 B2 US 7085339B2
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signal
data
synchronous
data recovery
lock
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US20020122517A1 (en
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Chul-Jin Kim
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Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/04—Speed or phase control by synchronisation signals
    • H04L7/10—Arrangements for initial synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0054—Detection of the synchronisation error by features other than the received signal transition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
    • H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
    • H04L7/0334—Processing of samples having at least three levels, e.g. soft decisions

Definitions

  • the present invention relates to data recovery devices, and more particularly, to a data recovery device for recovering transmitted data by tracing timings of a transmission signal and detecting symbols on data streams of the signal in a forward control channel of a mobile telephone system.
  • an advanced mobile telephone system which is an analogue cellular mobile telephone system
  • the processes of set-up and hand-over (or hand-off) speech paths are performed through data transmission/reception between a base station and a mobile station (or a terminal).
  • AMPS advanced mobile telephone system
  • an analogue cellular telephone system sets up a speech path by commands from a base station and responses from a mobile station.
  • the AMPS protocol comprises transmitting control data from a base station to a mobile station (or terminal) through a forward control channel (FOCC or paging channel).
  • the control data is converted into binary digital data using an NRZ (Non-Return-to-Zero) pattern.
  • the binary digital data is converted into digital data streams encoded in a Manchester format, thereby being synchronized with timing clocks (or bit clocks), before being RF—transmitted through an air space (or a free space).
  • FIG. 1 shows a structure of an NRZ (Non-Return-to-Zero) data stream on a FOCC.
  • An NRZ data stream comprises a 10-bit dotting portion, a 11-bit synchronizing portion, and a plurality of blocks of 44-bit data in a predetermined series.
  • the series of 44-bit data blocks has two data types for service systems A and B, and the 44-bit data blocks for A and B service systems are alternatively provided to the data stream five times.
  • the data stream further comprises busy/idle bits supplied thereto by ten bits.
  • FIG. 2 is a timing diagram that illustrates signal waveforms for the transmission/recovery of a signal on a FOCC or paging channel.
  • a base station encodes an original signal having the NRZ data stream into a Manchester format, synchronously in response to a bit clock of 10 KHz.
  • the Manchester-encoded signal is modulated to form a carrier wave signal, and the modulated signal is transmitted to a mobile station through air.
  • the mobile station demodulates the carrier wave signal, and converts the demodulated signal into the original signal having the NRZ data steam by timing and tracing the demodulated signal based on a sampling period, for example, 40 KHz.
  • FIG. 3A shows waveforms of a synchronous signal (Sync) of a demodulated signal to be recovered according to a conventional data recovery protocol.
  • FIGS. 3B–3E show synchronous signals of the demodulated signal illustrating a soft decision for recovering data.
  • FIG. 3B when the demodulated signal transitions from a positive domain to a negative domain, a bit of NRZ data corresponding to the signal is set to “0” (logically low in binary) if a summation result of the level point values is positive (>>0).
  • FIG. 3B shows waveforms of a synchronous signal (Sync) of a demodulated signal to be recovered according to a conventional data recovery protocol.
  • FIGS. 3B–3E show synchronous signals of the demodulated signal illustrating a soft decision for recovering data.
  • FIG. 3B when the demodulated signal transitions from a positive domain to a negative domain, a bit of NRZ data corresponding to the signal is set to “0” (logically low in
  • a bit of the NRZ data corresponding to the signal is set to “1” (logically high in binary) if a summation result of the level point values is negative ( ⁇ 0).
  • a conventional data recovery protocol may cause an error in tracing and sampling the demodulated signal using a synchronous signal, if the demodulated signal has a phase shift (e.g., to left) at a certain time, Tps, such as shown in FIG. 3A during the signal transmission through the air interface.
  • the demodulated signal is sampled by 40 KHz in every cycle period of the synchronous signal (Sync).
  • the synchronous signal at cycle period P 9 may have abnormal level points a′, b′, c′, and d′, as shown in FIGS. 3C and 3E .
  • a summation value of the level points i.e., ⁇ ( ⁇ a′) ⁇ b′+c′+d′ ⁇ , results in a negative value, and thus the bit of the NRZ data corresponding to cycle period P 9 is erroneously set to “1”.
  • FIG. 3C a summation value of the level points, i.e., ⁇ ( ⁇ a′) ⁇ b′+c′+d′ ⁇ , results in a negative value, and thus the bit of the NRZ data corresponding to cycle period P 9 is erroneously set to “1”.
  • the summation value of the level points i.e., ⁇ a′ ⁇ ( ⁇ b′)+( ⁇ c′)+( ⁇ d′) ⁇ results a positive value, and thus the bit of the NRZ data corresponding to cycle period P 9 is erroneously set to “0”.
  • the abnormal sampling of the demodulated signal using the synchronous signal typically occurs due to fading effects that disaccord synchronization states of the demodulated signal.
  • the data recovery process at a communication system is not only an important factor in evaluating the performance of data processing in the system, but also an important factor in affecting an error bit rate (BER) thereof.
  • BER error bit rate
  • a data recovery device comprises a demodulator for demodulating a transmission signal, a plurality of symbol recovery units, each generating a corresponding synchronous signal and a lock signal, wherein the lock signals are selectively enabled to select one of the synchronous signals, based on pattern variations of the transmission signal detected by the symbol recovery units, and a data decision unit for performing a data recovery operation using the selected synchronous signal to recover original data of the transmission signal.
  • the device further comprises a level controller for limiting a voltage range of the demodulated signal to a predetermined voltage range.
  • the data decision unit performs the data recovery operation by sampling the demodulated signal using a predetermined frequency within each cycle of a selected one of the synchronous signals.
  • a data recovery device for a mobile communications system comprises a demodulator for demodulating a transmission signal, a level controller for controlling voltage levels of the demodulated signal, a plurality of symbol recovery units, each generating a synchronous signal and a lock signal, a data recovery unit for performing a data recovery operation using a selected one of the synchronous signals, and a lock switch for selecting one of the synchronous signal, in response to the activation of a corresponding lock signal.
  • a method for recovering data in a communications system comprises the steps of demodulating a transmission signal, tracking signal patterns of the demodulated signal to generate a plurality of synchronous signals, selecting one of the synchronous signals based on a detected phase variation of the demodulated signal, and recovering data from the demodulated signal using the selected synchronous signal.
  • a program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for recovering data in a communications system.
  • the method steps comprise the steps of demodulating a transmission signal, tracking signal patterns of the demodulated signal to generate a plurality of corresponding synchronous signals and lock signals, selectively activating the lock signals based on a detected phase variation of the demodulated signal to selected one of the synchronous signals, and recovering data from the demodulated signal using the selected synchronous signal.
  • FIG. 1 is a diagram illustrating a structure of a NRZ data stream on a FOCC of AMPS.
  • FIG. 2 is a timing diagram illustrating a conventional method for transmission/recovery of a NRZ data stream.
  • FIGS. 3A through 3E are diagrams showing waveforms for recovering data from a demodulated signal according to a conventional data recovery device and method.
  • FIG. 4 is a block diagram of a data recovery device according to an embodiment of the present invention.
  • FIG. 5 is a timing diagram illustrating a method for recovering data according to an embodiment of the present invention.
  • FIG. 4 is a block diagram of a data recovery device according to an embodiment of the present invention.
  • the data recovery device may be incorporated in a communication system such as a mobile station.
  • the data recovery device comprises a demodulator 101 , a level controller 103 , a pair of symbol recovery units 105 and 107 , a lock switch 109 , and a data decision unit 111 .
  • the demodulator 101 receives and converts a transmission signal into a demodulated signal having a base band.
  • the transmission signal is formed by encoding original data having an NRZ data stream structure in a Manchester pattern.
  • the level controller 103 establishes voltage levels from the demodulated signal to prepare for the sampling and symbol detection operations, excluding an intermediate voltage range from the sampling range including the level points a, b, c, and d based on the sampling frequency 40 KHz.
  • the symbol recovery units 105 and 107 detect signal patterns output from the level controller 103 , and then generate symbol synchronous signals (S 1 and S 2 ), respectively.
  • the symbol synchronous signals (S 1 and S 2 ) are alternatively applied to the data decision unit 111 through the lock switch 109 in response to synchronous lock signals (SL 1 and SL 2 ), respectively.
  • the symbol synchronous signal (S 1 ) is used in recovering original data in response to the lock signal (SL 1 ), while the symbol synchronous signal (S 2 ) is used in recovering the original data in response to the lock signal (SL 2 ).
  • the data decision unit 111 generates NRZ data stream (that is subsequently recovered to the original data) preferably using the soft decision process as shown in FIGS. 3B and 3D .
  • FIG. 5 is a timing diagram illustrating a data recovery method according to an embodiment of the invention.
  • original data comprising an NRZ data stream format encoded in Manchester format is transmitted from a base station to a mobile station by means of a RF carrier wave signal.
  • the demodulated signal output from the demodulator 101 has an abnormal phase variation (shifted to left) by a certain time, Tps, due to fading effects or conditions at the base station, for example.
  • the level controller 103 truncates the demodulated signal from the demodulator 101 to establish voltage levels for sampling and symbol detection of the signal.
  • the level controller 103 further excludes an intermediate voltage range that is unnecessary to define the pattern of the demodulated signal.
  • One of the symbol recovery units e.g., the first symbol recovery unit 105 , checks signal patterns of the demodulated signal and generates a symbol synchronous signal (S 1 ).
  • the data decision unit 111 performs a data recovery operation using the symbol synchronous signal (S 1 ) in response to the lock signal (SL 1 ).
  • the data recovery operation is preferably performed using the soft decision process (as shown in FIGS. 3B and 3D ) with the level points a ⁇ d, based on a sampling frequency, for example, 40 KHz.
  • the lock signal (SL 1 ) is disabled and another lock signal (SL 2 ) is enabled. That is, at the time Tps when the phase variation occurs, the locking status of the demodulated signal is changed from the symbol synchronous signal (S 1 ) to the symbol synchronous signal (S 2 ).
  • the decision unit 111 performs a data recovery operation using the symbol synchronous signal (S 2 ) and the soft decision process.
  • the abnormal phase variation will occur gradually instead of abruptly as shown in FIG. 5 (or FIG. 3A ).
  • the switching of the data recovery operation between the symbol synchronous signals (S 1 and S 2 ) occurs whenever a phase variation occurs on the demodulated signal.
  • the sampling frequency i.e., 40 KHz
  • the level points may be modified to obtain more precise sampling and detection.
  • the number of the symbol synchronous signals may be modified as described to achieve more precise sampling and detecting of the demodulated signal.
  • the data decision unit 111 After completing the data recovery operations, the data decision unit 111 generates the NRZ data stream in accordance with a bit clock, preferably having a period of 0.1 ms.
  • a data recovery device improves a reliability of a data recovery operation even if a transmission signal has phase variations due to fading or other environment effects. Further, the switching of the data recovery operation of the invention can reduce bit error rate (BER) of the transmission signal in various environments of wireless communication system, particularly in FOCC of an AMPS.
  • BER bit error rate

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
  • Dc Digital Transmission (AREA)
  • Mobile Radio Communication Systems (AREA)
US10/091,059 2001-03-05 2002-03-05 Data recovery device Expired - Lifetime US7085339B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR2001-11132 2001-03-05
KR10-2001-0011132A KR100414208B1 (ko) 2001-03-05 2001-03-05 데이터 복구장치

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4791199B2 (ja) * 2006-02-09 2011-10-12 富士通セミコンダクター株式会社 同期装置及び同期方法
JP5413969B2 (ja) * 2007-03-20 2014-02-12 スパンション エルエルシー プロセッサ・システム最適化支援装置、および支援方法
US8666001B2 (en) * 2011-07-15 2014-03-04 Motorola Solutions, Inc. Method and apparatus for updating symbol recovery parameters and correcting symbol timing misalignment

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5204879A (en) * 1991-01-31 1993-04-20 Motorola, Inc. High speed data detection and clock recovery in a received multi-level data signal
US5521941A (en) * 1990-11-29 1996-05-28 Motorola, Inc. Automatic threshold control for multi-level signals
US5859671A (en) * 1995-06-09 1999-01-12 Samsung Electronics Co., Ltd. Symbol timing recovery circuit and method
US6134276A (en) * 1998-03-31 2000-10-17 Lucent Technologies Inc. Timing recovery system
US6504838B1 (en) * 1999-09-20 2003-01-07 Broadcom Corporation Voice and data exchange over a packet based network with fax relay spoofing

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5182761A (en) * 1991-01-31 1993-01-26 Motorola, Inc. Data transmission system receiver having phase-independent bandwidth control
US5299235A (en) * 1991-09-10 1994-03-29 Telefonaktiebolaget L M Ericsson Time synchronization of a receiver in a digital radio telephone system
KR950026141A (ko) * 1994-02-08 1995-09-18 이헌조 심볼 타이밍 보상 장치
US6058150A (en) * 1997-09-30 2000-05-02 Wireless Access, Inc. Method and apparatus for combined timing recovery, frame synchronization and frequency offset correction in a receiver
JP3565729B2 (ja) * 1998-01-21 2004-09-15 富士通テン株式会社 同期タイミング再生装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5521941A (en) * 1990-11-29 1996-05-28 Motorola, Inc. Automatic threshold control for multi-level signals
US5204879A (en) * 1991-01-31 1993-04-20 Motorola, Inc. High speed data detection and clock recovery in a received multi-level data signal
US5859671A (en) * 1995-06-09 1999-01-12 Samsung Electronics Co., Ltd. Symbol timing recovery circuit and method
US6134276A (en) * 1998-03-31 2000-10-17 Lucent Technologies Inc. Timing recovery system
US6504838B1 (en) * 1999-09-20 2003-01-07 Broadcom Corporation Voice and data exchange over a packet based network with fax relay spoofing

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US20020122517A1 (en) 2002-09-05
JP2002300140A (ja) 2002-10-11
KR20020071160A (ko) 2002-09-12
KR100414208B1 (ko) 2004-01-07
JP4485736B2 (ja) 2010-06-23

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